1. Field of the Invention
The present invention relates to the technology fields of liquid crystal display, and in particular to a gamma voltage driving circuit, a source driving module, and a liquid crystal panel comprising the source driving module in the liquid crystal display.
2. The Related Arts
Liquid crystal display (LCD) is a flat and thin display device. It is consisted of color or monochrome pixels with a certain amount, which is placed in front of the light source or the reflector. Liquid crystal display has low power consumption, high image quality, small size, and light weight, so it is favored to become the mainstream of display. The existing liquid crystal display is mainly thin film transistor (TFT) liquid crystal display, and the liquid crystal panel is the main component of the liquid crystal display.
FIG. 1 is a schematic view illustrating the structure of a liquid crystal panel, which comprises an upper glass substrate 1, a down glass substrate 2, and a liquid crystal layer 3 between the upper glass substrate 1 and the down glass substrate 2. One side of the liquid crystal layer 3 is provided with an ITO common electrode 4. The ITO common electrode 4 is connected to the Vcom voltage. The other side of the liquid crystal layer 3 is provided with multiple pixel electrodes 5. Each pixel electrode is connected to a Gamma voltage. The Gamma voltage is used to control the display grayscale of the liquid crystal panel. The voltage difference between different Gamma voltages and the Vcom voltage results in different rotation angles of liquid crystal, which forms the brightness difference. That is, the Gamma voltage divides the changing process from white to black into 2n equal parts.
For example, FIG. 2 is a Gamma voltage driving circuit according to the prior art, which comprises a reference voltage module 10, a voltage dividing resistor string 20, and a voltage selecting module 30. The circuit corresponds to 3 bit binary code, that is, the voltage dividing resistor string 20 divides the reference voltage into 8 Gamma voltage V1˜V8 (divide the changing process from white to black into 23 equal parts), the voltage selecting module 30 selectively outputs one of the Gamma voltage. The voltage selecting module 30 is consisted of multiple MOS transistors 301. In the 3 bit driving circuit, each transmission line of the Gamma voltage provides with three MOS transistor, which is total 8*3=24 MOS transistors. In FIG. 2, when it selectively outputs the Gamma voltage V8, the corresponding binary code is (111), the voltage selecting module 30 turns on the MOS transistors b2, b1, and b0, and then the Gamma voltage V8 connects to the output terminal. In the driving circuit, when it utilizes 10 bit binary code, as shown in FIG. 3, the voltage dividing resistor string 20 divides the reference voltage into 1024 Gamma voltages V1˜V1024 (divide the changing process from white to black into 210 equal parts), the voltage selecting module 30 totally needs 1024*10=10240 MOS transistors 301. A large number of MOS transistors increase the difficulty of the design of driver IC and the production process, which increases the costs.